Optical communication is generally a form of communication that involves the transmission and reception of light. Typically in modern communication systems optical fiber is often the most common type of channel for optical communications, however, other types of optical waveguides are used within communications gear, and have even formed the channel of very short distance (e.g. chip-to-chip) links. Optical fiber often consists of a core, cladding, and an opaque protective outer coating, which guides light along the core by total internal reflection. The core, and the lower-refractive-index cladding, is typically made of high-quality silica glass, though they can both be made of plastic as well.
The transmitters in optical fiber links are generally light-emitting diodes (LEDs) or laser diodes. Infrared light, rather than visible light may be used in part, because optical fibers transmit infrared wavelengths with less attenuation and dispersion. The signal encoding is typically simple intensity modulation, although historically optical phase and frequency modulation have been demonstrated.
Modern fiber-optic communication systems generally include an optical transmitter to convert an electrical signal into an optical signal to send into the optical fiber, a fiber-optic cable routed through conduits (often underground conduits) and buildings, multiple kinds of amplifiers, and an optical receiver to recover the signal as an electrical signal. The information transmitted is typically digital information generated by computers, telephone systems, and cable television companies.